The subject matter of the present invention is dialkoxy titanium(IV)acetylacetonates which have the known typical properties of these chelated titanium compounds, but do not have the otherwise common red color.
It is known to use titanium chelates, especially dialkoxytitanium(IV)-bis-acetylacetonates, which are also referred to hereinafter as titanium acetylacetonates, as catalysts, crosslinking agents or coating materials, advantage being taken especially of the fact that their reactivity is lower than that of the tetraalkyl titanates, such as tetraisopropyltitanate for example, and of their reduced sensitivity to hydrolysis. This is important mainly in cases in which the intended catalytic or crosslinking action in a mixture of components is not to take place until a later moment in time, that is, after a period of standing. Practical examples of this can be considered to be flexographic printing inks on the basis of nitrocellulose, or slurries on the basis of titanium acetylacetonate for the production of fine casting molds; in any case, the hardening or crosslinking is not to take place in the container, which would undoubtedly happen with tetraalkyltitanates, but not until after the printing is performed, in the one case, or after the application of a coating to a model in the other.
Titanium acetylacetonates are commonly used in the form of an approximately 75% solution in the alcohol corresponding to the alkoxy groups of the chelate--usually isopropanol--directly as produced from one mole of tetraalkyltitanate and two moles of acetylacetone. The best-known representative of these titanium acetylacetonates is diisopropoxytitanium(IV)-bis-acetylacetonate.
These known titanium acetylacetonates are more or less red-colored due to circumstances of their manufacture. The intense red solution is usable for many applications (concentration by evaporation results in handling problems on account of orange-colored precipitates), but in other applications, such as the formulation of white or light-colored flexographic printing inks, the natural color is definitely undesirable.
The simple remedy of lowering the amount of acetylacetone to slightly less than two moles per gram-atom of titanium in the preparation of the titanium acetylacetonate, thus losing some of the stability of the chelate, but producing a yellow solution, does not give lasting results: after standing a while, the solution turns red again, and precipitation can occur. If the amount of acetylacetone is reduced excessively, say to 1.5 moles or less, titanate solutions are obtained which, although they are yellow, not red, their performance is much like that of the reactive and hydrolysis-sensitive tetraalkyltitanates.
The problem therefore was to find titanium chelates which would have the properties of the titanium acetylacetonates but would not be so strongly colored as these chelates are.